1. Field of Invention
This invention relates to a grommet that engages around an outer periphery of a wire harness for an automobile and is mounted in a through hole of an automobile body panel. In particular, this invention improves seal efficiencies by providing plural contact points between the automobile body panel and the grommet.
2. Description of Related Art
Conventionally, when a wire harness for an automobile is inserted into a through hole provided in an automobile body panel that divides an engine compartment and a passenger compartment, in order to wire the wire harness, the wire harness is inserted into a grommet which is made of a rubber. The grommet is provided with a generally conical (convex) portion with a recess for engaging with the automobile body and a small-diameter cylindrical portion that extends from the tip end of the conical portion and tightly engages around an outer peripheral surface of the wire harness. Then, the grommet with the wire harness is mounted in the through hole. The recess for engaging with the automobile body contacts the edge of the through hole of the automobile body panel to prevent water intrusion from the through hole.
When a burring is not protrusively provided around the through hole of the automobile body panel, a grommet 1 as shown in FIGS. 6(A)-6(C) is used. The grommet 1 is provided with a small-diameter cylindrical portion 1a to tightly cover a wire harness, a generally conical portion 1b extending from one end of the small-diameter cylindrical portion 1a. A conical portion has a thickened portion around an enlarged end of the conical portion. The recess 1c for engaging with an automobile body panel is provided on an outer periphery of the thickened portion. One side wall 1g of the recess in the enlarged end of the conical portion extends outwardly and a lip 1d is provided on the tip of the extending side wall.
A width W1 of the recess 1c (the distance between side walls if and 1g) is defined to be slightly larger than a panel thickness W2 of an automobile body panel 2 to make the grommet easier to mount on the automobile body panel and to provide versatility such that the grommet can be used with an automobile body panel having a variety of the panel thicknesses W2. As described above, the lip 1d is provided and pressed against the automobile body panel 2. Further, the diameter D1 of the grommet around the bottom surface 1e of the recess 1c is defined such that an entire inner peripheral surface 2a-2 of the through hole 2a contacts the bottom surface 1e of the recess 1e. In other words, the diameter D1 is defined to be at least as large as the diameter D2 of the through hole 2. More specifically, when D2 is 55 mm, D1 is set to be about 55 mm plus 0 mm to 0.3 mm.
Thus, to secure a seal efficiency, the recess 1c of the grommet 1 and the automobile body panel 2 which engages with the inner surface of the recess 1c, contact each other at three points P1, P2 and P3 as shown in FIG. 6(C). In other words, the entire inner peripheral surface 2a-2 of the through hole 2a contacts the bottom surface 1e of the recess 1c at P1, the lip 1d contacts panel 2 at P2, and the automobile body panel 2 is pressed against the side wall 1f of the recess 1c at P3 by the lip 1d. 
However, as shown in FIG. 7, for example, when a wire harness fitted with the above-described grommet is inserted into the through hole 2a from an engine compartment side (X) to a passenger compartment side (Y), the wire harness is often forced to bend in the engine compartment side (X). Thus, when the wire harness W/H is bent, the grommet 1, which is fixed to the wire harness by taping at the small-diameter cylindrical portion 1a, is also forced to bend. Therefore, at a side opposite to the bending direction ((Z) in FIG. 7), as shown in FIG. 8, the inner peripheral surface 2a-2 of the through hole 2a becomes separated from the bottom surface 1e of the recess 1c. In addition, the side wall if on the small-diameter cylindrical portion side is pulled and is sometimes separated from the automobile body panel 2. Thus, only the lip 1d contacts the automobile body panel 2, and the original three contact points for sealing are reduced to one. As a result, water can easily enter the passenger compartment side (Y) and, in the worst case, water does intrude into the passenger compartment side (Y).
Accordingly, the present invention is provided to overcome the above-described problems. The objective of the present invention is to provide a grommet that contacts the automobile body panel at plural points instead of only one sealing point in the lip and thus ensures waterproofness, even when the grommet is pulled in a direction due to bending of the wire harness.
To achieve the above and other goals, the present invention provides a grommet that engages around an outer periphery of a wire harness and is mounted on a through hole of an automobile body panel without burring. The grommet of the present invention includes a generally cylindrical portion that tightly covers wires of the wire harness. A generally conical portion extends from one end of the cylindrical portion. A thickened portion is provided around the conical portion in an enlarged end. A recess for engaging with the automobile body is provided on the outer peripheral surface of the thickened portion. A first side wall of the recess in the enlarged end extends outwardly, and a lip projects from a tip of the first side wall. A bottom surface of the recess has one of a curved portion and an inclined portion so that an edge of the through hole is forcefully pressed into and distorts the curved or inclined portion. A second side wall of the recess faces the first side wall and is formed so as to approach the first side wall along a direction from the bottom surface to an opening end of the recess. Thus, the automobile body panel, which engages with the inner surface of the recess of the grommet of the present invention, contacts the curved portion or inclined portion of the recess and the second side wall, as well as the lip
As described above, the bottom surface of the recess configured to be engaged with the automobile body has a curved or inclined portion, and the edge of the through hole is forcefully pressed into and distorts the curved or inclined portion. Therefore, even if the grommet is pulled in a direction such that the inner peripheral edge of the through hole is separated from the bottom surface of the recess, the inner peripheral edge of the through hole engages and remains in contact with the curved or inclined surface. Further, since the side wall that faces the lip-side side wall is formed so as to approach the lip-side side wall, the automobile body panel is pressed by the lip and contacts the side wall that faces the lip-side side wall. Accordingly, together with the contact between the lip and the automobile body panel, the grommet and the automobile body panel remain in contact with each other at three points.
When the grommet is strongly pulled and sharply bent, the side wall that faces the lip-side side wall may be pulled in the bending direction and may be separated from the automobile body panel. Even in that case, since the bottom surface of the recess is curved or inclined in a V-shape, and the inner peripheral edge of the through hole is forcefully pressed into and distorts the curved or inclined bottom surface, the contact therebetween is maintained. Thus, together with the contact by the lip, at least two contact points are ensured. Accordingly, unlike the prior art device, since there is no chance for the grommet of the present invention to contact with the automobile body panel at only one contact point, seal efficiency is improved compared with the prior art device.
In accordance with another aspect of the present invention, the lip projects in a direction toward the cylindrical portion side and the lip projects a distance greater than a width between the first and second side walls at the opening end of the recess. Accordingly, the lip presses the automobile body panel more forcefully toward the cylindrical portion side, and thus, the contact between the lip and the automobile body is ensured.
According to a further aspect of the present invention, a maximum width of a gap between the first side wall and the second side wall is at least as large as the panel thickness of the automobile body panel so that the grommet can be used with an automobile body panel having a variety of panel thickness.
According to another aspect of the present invention, a width of a gap between the first side wall and the second side wall at the opening end of the recess is at least as large as the panel thickness of the automobile body panel. Accordingly, the opening end of the recess firmly contacts the automobile body panel.
In another aspect of the present invention, a diameter of the grommet around the bottom surface of the recess is at least as great as a diameter of the through hole. Accordingly, the edge of the through hole firmly engages with the bottom surface.
In accordance with a further aspect of the present invention, one of the curved portion and the inclined portion is provided in a side of the second side wall on the bottom surface of the recess. One of the curved portion and the inclined portion can also be provided in both sides of the first and second side walls on the bottom surface of the recess.